In an event processing system an ‘event’ is an identifiable occurrence that has some significance, for example, from a business perspective a business event is a customer placing an order for goods and from a technical perspective, a technical event is the detection of a hardware device malfunctioning.
A significant element of event processing is the task of processing multiple events, whether these are business events or technical events, in order to identify events that are of interest. Event processing software may monitor for events and look for certain event patterns that may be of interest to the user. Once identified, an event may trigger a further action of the event processing system. For example, if a share price reaches/or drops to a particular price, the data processing system may trigger a sale of the share(s).
In an event processing system, the function of identifying events is performed by an event emitter and the generation of an action in response to the emitted event, is performed by a function called an event consumer. There may be many event emitters and event consumers in an event processing system. An event processing system may, for example, comprise a telecommunication network and an event emitter may be a sensor or a probe associated with a piece of hardware. The event consumer may generate an alert in response to the event emitter receiving a signal from the sensor of the probe that there is a fault with the piece of hardware which is being monitored.
It is known, in an event processing system, for an event to occur as a result of a change in a scalar value, for example, a change in the number of active transactions the scalar value) in the event processing system. An example is as follows:    The number of active transactions is value X    The number of active transactions is determined to be high    The number of active transactions is now determined to be decreasing in number    The number of active transactions has risen above 80% of the predetermined maximum active limit
Event processing systems typically provide a means in which a user, of the event processing system, can configure the one or more event emitters to identify particular events of interest. Therefore, logic within the event emitter performs a filter operation in order to identify whether a detected event is an event of interest to the user. If the event is determined to be of interest to the user, the event emitter generates an event for receiving by an event consumer. The event consumer takes some form of action which is appropriate to the event generated by the event emitter.
Prior art US 20100023598, discloses monitoring the performance, security and health of a system in an industrial application. Agents report data to an appliance or server. The appliance stores the data and determines when an alarm condition has occurred. Alarm thresholds may be user defined.